[19446] in Kerberos_V5_Development
Securing the keytabs of host-based principals
daemon@ATHENA.MIT.EDU (John Devitofranceschi)
Wed Jul 6 07:26:06 2016
From: John Devitofranceschi <jdvf@optonline.net>
Message-Id: <0719B5D6-FD90-4B81-89FF-61845A4741D1@optonline.net>
Date: Wed, 6 Jul 2016 07:25:56 -0400
To: "krbdev@mit.edu Dev List" <krbdev@mit.edu>
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It is a common convention to have service principal names of the form =
service/fqdn@REALM.
It is also common for these SPNs to have keytab files on the servers =
that run the services they=E2=80=99re associated with.
Sometimes it is necessary for these keytabs to be used for =
authentication.
I was thinking that is would be a good thing to be able to verify that =
an authentication request for a principal like service/fqdn was =
actually coming from the fqdn in the principal name. Certainly this =
check can be done by looking at the ISSUE KDC log message since both the =
requesting principal name and the requesting ip address are in the log. =
But by then it=E2=80=99s too late.
Would it be possible/desirable/sensible to have a new attribute (or =
flag) that designates a principal to be a host-based principal that =
follows standard conventions? When the KDC sees a ticket request from a =
principal with this attribute, an additional check will verify that the =
source address of the request maps to the fqdn in the principal.
Additionally a kdc.conf variable could be defined that controls the =
behavior of this check when it fails: warn (the default) or deny.
This would allow operators to (at least) easily detect if any keytabs =
are being used on hosts for which they were not intended.=20
jd
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